Library classification disappeared. How to return the original classification
My library classification itself disappeared, how to return to the previous original classification, I have been keeping the habit of synchronization, how to return to yesterday's classification
Are you referring to Zotero collections?
It looks like you deleted a couple collections in your library in the last week. If you did that by mistake, and this happened recently, you might be able to restore from one of the automatic backups. Note the specific instruction about collections.
Two other collections were deleted — both in the last hour — so those should certainly be in your last automatic backup. Make sure you're carefully following the instructions to temporarily disable auto-syncing.
Dozens of other items in your library were deleted a couple days ago, both no other collections have been deleted in over a month.
To be clear, these would only be changes that you or someone else with access to your account (e.g., on a shared computer where you left yourself logged in) made. There's no way for changes to be made to your library otherwise.
https://www.zotero.org/support/zotero_data#restoring_from_the_last_automatic_backup